Process for producing graphite and vertical graphitization furnace

ABSTRACT

A process for producing graphite in a vertical graphitization furnace having at least one process chamber that bounds a heating zone, a temperature of 2200° C. to 3200° C. is generated in the heating zone, particulate graphitizable material is supplied to the process chamber through an inlet, graphitizable material is conveyed through the heating zone of the process chamber, in which it is graphitized to graphite, and graphite obtained is removed from the process chamber through an outlet. In some variants, graphitizable material wherein the particles have a particle size of less than 3 mm is used, and/or, a material column is formed throughout the heating zone of a particular process chamber, wherein graphitizable material, after being supplied through the inlet from the top, trickles through an intake zone of the process chamber onto the material column, and/or, a material column is formed in a stationary heating zone of a particular process chamber encompassed by the heating zone, wherein graphitizable material, after being supplied through the intake from the top, trickles through a drop heating zone likewise encompassed by the heating zone onto the material column, and/or, graphitizable material in one or more material vessels is conveyed through a particular process chamber and through the heating zone thereof. Also specified is a vertical graphitization furnace optimized.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates to a process for producing graphite in a verticalgraphitization furnace having at least one process space which delimitsa heating zone, in which

-   a) a temperature of from 2200° C. to 3200° C., in particular of from    2700° C. to 3200° C., preferably of 3000° C., is generated in the    heating zone;-   b) particulate graphitizable material is fed through an entrance    into the process space;-   c) graphitizable material is conveyed through the heating zone of    the process space, in which it is graphitized to give graphite;-   d) graphite obtained is discharged from the process space through an    exit.

The invention further relates to a vertical graphitization furnacehaving at least one process space which delimits a heating zone,comprising

-   a) a heating device by means of which a temperature of from 2200° C.    to 3200° C., in particular of 3000° C., can be generated in the    heating zone;-   b) a feed conveyor by means of which particulate graphitizable    material can be fed through an entrance into the process space;    where-   c) graphitizable material can be conveyed through the heating zone    of the process space, in which it is graphitized to give graphite;-   d) an output conveyor is present, by means of which graphite    obtained can be discharged from the process space through an exit.

2. Description of the Prior Art

The graphitization of graphitizable material is carried out in an inertgas atmosphere. It is known that polycrystalline graphite, which is usedfor anode material, can be produced in batch processes in so-calledAcheson furnaces in which graphitizable material is graphitized to givegraphite.

In addition, graphitizing graphitizable material having large particlediameters of more than 3 mm in vertical graphitization furnaces of thetype mentioned at the outset to give graphite is known from EP 2 980 017B1. After this process, the graphite obtained, which has particles whichare too large for anode material, has to be comminuted to give agraphite powder.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a process and a verticalgraphitization furnace of the type mentioned at the outset which areenergy-efficient and make a largely constant and reproducible graphitequality possible.

This object is achieved in a process of the type mentioned at the outsetby,

-   as variant A, graphitizable material whose particles have a particle    size of less than 3 mm being used;    and/or-   as variant B, a column of material being formed in the total heating    zone of a particular process space, with graphitizable material    which has been fed in through the entrance trickling from the top    through an inlet zone of the process space onto the column of    material;    and/or-   as variant C, a column of material being formed in a standing    heating zone of a particular process space, said standing heating    zone being encompassed by the heating zone, and graphitizable    material which has been fed in through the entrance trickling from    the top through a falling heating zone, which is likewise    encompassed by the heating zone, onto the column of material;    and/or-   as variant D, graphitizable material being conveyed in one or more    containers for material through a particular process space and    through the heating zone thereof.

It has been recognized according to the invention that the above objectis achieved in the process of the type mentioned at the outset by meansof a number of approaches which, when employed either alone or in asynergistic combination or, if a graphitization furnace having aplurality of process spaces is utilized, in parallel, contribute to amore effective process procedure compared to the prior art. Sincevariants A, B, C and D can also be carried out in parallel, mention mayin each case be made in the case of variants B, C and D and in thefollowing of a “particular” process space. This is intended to expressthe fact that in the case of optionally a plurality of process spaces ina furnace, one particular process space is under consideration. This canalso be, but does not have to be, a process space in which anothervariant proceeds, as long as these can proceed simultaneously; this isnot possible in the case of variants B and C.

Variant A makes it possible, in the most favorable case, to dispensewith a subsequent comminution of the graphite obtained. In any case, theoutlay for satisfactory comminution can be reduced.

Variant B allows a continuous process in a defined atmosphere.

In variant C, a type of preheating can occur in the falling heatingzone, so that the energy consumption for heating the column of materialwhich is then formed from the already preheated graphitizable materialis reduced.

In variant D, smaller volumes are graphitized in the containers formaterial, as a result of which process control is improved.

To achieve a constantly controllable process, it is advantageous for thesame volume of graphitizable material to be fed into a particularprocess space per unit of time as the volume of graphite which isdischarged from this process space per unit of time.

The graphitizable material can be fed continuously or intermittentlyinto a particular process space and graphite can be dischargedcontinuously or intermittently from this process space, with preferencebeing given to continuous feeding and discharge. In the case of anintermittent process, feeding and discharge can be carried outsimultaneously or offset in time.

In order to carry out process variants B and C reproducibly, it isadvantageous for a fill level of the column of material to be keptlargely constant in the case of variant B and/or in the case of variantC.

To control and monitor the preheating in the case of variant C, it canbe advantageous for a gas to be blown in countercurrent opposite to orin a flow in the falling direction of the graphitizable material intothe falling heating zone.

As already indicated above, it is possible to use a graphitizationfurnace which has a plurality of process spaces and whose plurality ofprocess spaces are operated in parallel in time.

In respect of variant A, it is advantageous for the particles of thegraphitizable material to have an average particle diameter of greaterthan 5 μm and less than 3000 μm, less than 2500 μm, less than 2000 μm,less than 1500 μm, less than 1000 μm or less than 500 μm, or in that theparticles of the graphitizable material to have an average particlediameter of from 5 μm to 3000 μm, from 500 μm to 2000 μm or from 1000 μmto 1500 μm.

For effective operation, it is advantageous for the temperature of theheating zone to be determined, in particular at the upper end of theheating zone and/or in approximately the middle of the heating zoneand/or at the lower end of the heating zone and/or at the column ofmaterial of each process tube present. In this way, account can quicklybe taken of temperature fluctuations in the heating zone by controllingthe heating device in such a way that undesirable temperature changesare compensated for.

In the vertical graphitization furnace of the type mentioned at theoutset, the object indicated is achieved by

-   e) the heating zone in at least one process space comprising a    falling heating zone and a standing heating zone which are    configured such that a column of material is formed in the standing    heating zone and graphitizable material which has been fed in    through the entrance can trickle from the top through the falling    heating zone onto the column of material;    and/or-   f) a transport system being present, by means of which graphitizable    material can be conveyed in one or more containers for material    through at least one process space and through the heating zone    thereof.

This optimizes the graphitization furnace, especially in respect ofprocess variants C and D.

In this case, it is advantageous in the transport system for the feedconveyor and the output conveyor to be configured in such a way thatthey transport containers for material containing material, and for thetransport system to comprise a process space conveyor which isconfigured in such a way that it conveys containers for material fromthe entrance to the exit.

The vertical graphitization furnace can be operated particularlyeffectively when the transport system is a loop transport system andadditionally comprises a connecting conveyor by means of whichcontainers for material can be conveyed from the output conveyor to thefeed conveyor.

The containers for material are advantageously crucibles having acrucible lid.

As explained above, it is advantageous for a plurality of process spacesto be present in the graphitization furnace.

Furthermore, a temperature monitoring device is advantageous, by meansof which it is possible to determine the temperature of the heatingzone, in particular at the upper end of the heating zone and/or inapproximately the middle of the heating zone and/or at the lower end ofthe heating zone and/or at the column of material of each process tubepresent.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will be explained in more detailbelow on the basis of the drawings, in which:

FIG. 1 shows a vertical graphitization furnace according to a firstexemplary embodiment in which graphitizable material is conveyed ascolumn of material from the top downward through a process space,illustrating a first way of carrying out the process;

FIG. 2 shows the vertical graphitization furnace of FIG. 1, illustratinga second way of carrying out the process;

FIG. 3 shows a vertical graphitization furnace according to a secondexemplary embodiment having two process spaces which run parallel;

FIG. 4 shows a modification of the exemplary embodiment of FIG. 3, inwhich the process spaces which run parallel are at a distance from oneanother;

FIG. 5 shows a vertical graphitization furnace according to a thirdexemplary embodiment having a transport system for containers formaterial in which graphitizable material is located.

DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS

FIG. 1 shows a vertical graphitization furnace 10 which is used forproducing polycrystalline graphite 12 for anode material and willsubsequently be referred to merely as furnace 10. Particulategraphitizable material 14 serves as starter material for the productionof the polycrystalline graphite 12. Graphitizable materials containcarbon, with conversion of amorphous carbon into polycrystallinegraphite occurring during graphitization. Examples of graphitizablematerials are brown coal or hard coal and optionally also polymers.

The particles of the graphitizable material 14 preferably have have aparticle size of less than 3 mm. The particles of the graphitizablematerial 14 preferably have an average particle diameter of greater than5 μm and less than 3000 μm, less than 2500 μm, less than 2000 μm, lessthan 1500 μm, less than 1000 μm or less than 500 μm. As an alternative,the particles can have an average particle diameter of from 5 μm to 3000μm, from 500 μm to 2000 μm or from 1000 μm to 1500 μm.

The furnace 10 comprises a process tube 16 having an outer tube wall 18made of graphite, which in its interior space 20 accommodates a processspace 22 which delimits an inlet zone 24 arranged vertically at the top,an outlet zone 26 arranged vertically at the bottom and a heating zone28 which is arranged in between and in which the particles of thegraphitizable material 14 are graphitized to give graphite 12.

The upper end 28 a of the heating zone 28 is thus defined at thetransition of the inlet zone 24 to the heating zone 28; the lower end 28b of the heating zone 28 is correspondingly defined at the transition ofthe heating zone 28 to the outlet zone 26. The interior space 20 or theprocess space 22 preferably have a circular cross section. However,alternative cross sections, for example elliptical or square orrectangular, are also possible. In general, the outer tube wall 18displays the geometry of the cross section of the interior space 20 orof the process space 22 and has a corresponding outer cross section;however, this can also be different therefrom.

The inlet zone 24 of the process tube 16 is joined at an entrance 30 toan exit side 32 of a feed conveyor 34 for the graphitizable material 14,the entrance side 36 of which is supplied with the graphitizablematerial 14 from a reservoir 38 for material. In the present exemplaryembodiment, the feed conveyor 34 is configured such that it conveys thegraphitizable material 14 as such and is for this purpose configured, inparticular, as screw conveyor, as is known per se. The outlet zone 24 ofthe process space 22 is correspondingly joined at an exit 40 to anentrance side 42 of an output conveyor 44 by means of which the graphite12 produced is taken off from the outlet zone 26 and discharged. In thepresent exemplary embodiment, the output conveyor 44 is configured suchthat it conveys the graphite 12 as such, for which purpose the outputconveyor 44 is likewise configured as screw conveyor. However, this isadditionally cooled with the aid of a water cooling system, as ishowever likewise known per se.

The feed conveyor 34 and the output conveyor 44 are configured in such away that a gastight connection to the process tube 16 can be formed andtransport can also be effected with exclusion of the ambient atmosphere.Alternative transport concepts, such as for example star feeders, doubleflap systems in combination with, for example, a conveyor belt or avibratory chute or the like, are also possible for this purpose.

In the region of the heating zone 28, the process space 16 is heated tofrom about 2200° C. to about 3200° C., preferably to about 3000° C., bymeans of a heating device 46 for the graphitization process, which isindicated in the figures merely by the darker hatched region of theprocess tube 16. The heating device 46 is in practice an electricheating device. For example, the wall thickness of the process tube 16is for this purpose reduced in the region of the heating zone 28, sothat the process tube 16 is more effectively heated up there due to thehigher electrical resistance. The heating zone 28 is defined by acontiguous section of the process space 22, in which essentially thesame graphitization temperature prevails.

The process tube 16 extends through a through-opening 48 of an uppercovering wall 50 and through a through-opening 52 of a lower bottom wall54 of an insulating housing 56 made of, for example, steel sheet, insuch a way that an upper end section 16 a of the process tube 16projects in an upward direction and a lower end section 16 b of theprocess tube 16 projects in a downward direction from the insulatinghousing 56. On the inside of the covering wall 50 and the bottom wall54, there are arranged in each case plate-shaped insulation elements 58,preferably made of hard graphite felt, with a passage 60 which isstepped in the axial direction for the process tube 16, which in eachcase define a step area 62. The respective region of the stepped passage60 having a smaller cross section is directed toward the covering wall50 or the bottom wall 54 of the insulating housing 56, so that the stepareas 62 face one another. The insulation elements 58 can be made in onepiece or be formed by two plate-shaped elements which havethrough-openings having different diameters, so that the stepped passage60 is formed overall.

A protective housing 64 made of graphite, for example a protective tube,for the process tube 16 extends from the step area 62 of the insulationelement 58 on the covering wall 50 to the step area 62 of the insulationelement 58 on the bottom wall 54 in such a way that an annular space 66,which is open at the top and bottom in the direction of thethrough-openings 48 and 52 of the covering wall 50 and the bottom wall54, respectively, is formed between the process tube 16 and theprotective housing 64.

An insulating annular space 68, which is bounded by the protectivehousing 64, the insulating housing 56 and the insulation elements 58, isformed radially next to the protective housing 64. This insulatingannular space 68 is filled with carbon black in the present exemplaryembodiment.

The through-opening 48 of the covering wall 50 is covered by means of anupper connection cap 70. In the present exemplary embodiment, the upperend section 16 a of the process tube 16 extends through the upperconnection cap 70, so that an upper annular connection space 72 isformed between the covering wall 50 of the insulating housing 56 and theentrance 30 of the process tube 16; this annular connection space 72 isfluidically connected via the through-opening 48 and covering wall 50and the passage 60 of the upper insulation element 58 to the annularspace 66.

In a corresponding way, the through-opening 52 of the bottom wall 54 iscovered by means of a lower connection cap 74. In the present exemplaryembodiment, the lower end section 16 b of the process tube 16 extendsthrough the lower connection cap 74, so that a lower annular connectionspace 76 is formed between the bottom wall 54 of the insulating housing56 and the exit 40 of the process tube 16; this annular connection space76 is in turn fluidically connected via the through-opening 52 of thebottom wall 54 and the passage 60 of the lower insulation element 58 tothe annular space 66.

At the upper and lower transitions between the insulating housing 56 andthe connection caps 70 and 74, there is a housing cooling device 78 toprotect the housing components, which is designed as a water coolingsystem, as is known per se.

The annular connection spaces 72 and 76, the annular space 66 and thepassages 60 of the insulation elements 58 form a gas space 80 which ispart of a protective gas system 82.

The protective gas system 82 further comprises a first protective gasinlet connection 84.1 on the upper connection cap 70 and a secondprotective gas inlet connection 84.2 on the lower connection cap 74,through which a protective gas can be blown into the gas space 80.

Since the insulation elements 58 are porous and thus gas-permeable,protective gas diffuses from the gas space 80 in the regions of thepassages 60 having a smaller cross section into the insulation elements58 and further into the insulating annular space 68. At the coveringwall 50 of the insulating housing 56, there is a protective gas outletconnection 86 so that the protective gas can be discharged. To assist, athird protective gas inlet connection 84.3 is also present on the bottomwall 54 of the insulating housing 56, so that protective gas can also beblown in a targeted manner into the insulating annular space 66.

The protective gas around the process tube 16 is necessary because thegraphitization of the graphitizable material 12 occurs under an inertgas atmosphere which is present in the process space 22. As protectivegas, use is generally made of the same gas as the inert gas, so that thesame type of gas is present on both sides of the outer tube wall 18 ofthe process tube 16. However, different gases can also be used asprotective gas and as inert gas, it being necessary for the protectivegas to also be inert. For example, argon, nitrogen or helium or amixture thereof can be used as protective gas and/or as inert gas.

In order to then introduce inert gas into the process space 22, theprocess tube 16 is coupled at the lower end section 16 b to an inert gasinlet connection 88 through which the inert gas can be blown into theprocess space 22. The upper end section 16 a of the process tube 16 isconnected to an offgas outlet connection 90, so that gases formed in thegraphitization mixed with inert gas can be drawn off as offgas from theprocess space 22. In this case, the furnace 10 is thus operated incountercurrent, with the inert gas flowing through the process space 22in the opposite direction to the direction of movement of the materialpresent in the process space 22. As an alternative, the inert gas inletconnection 88 can be arranged at the upper end section 16 a of theprocess tube 16 and the offgas outlet connection 90 can be arranged atthe lower end section 16 b of the process tube 16. In a furthermodification, in each case an inert gas inlet connection and an offgasoutlet connection can be connected to the process space 22 both at thetop and at the bottom, so that the graphitization can optionally becarried out in countercurrent or in cocurrent by appropriateswitching-over. The offgas is in each of these cases passed to thermalafter-combustion, as is known per se.

In a further modification, a gas supply tube can lead from an inert gasinlet connection 88 arranged at the upper end section 16 a in a downwarddirection to just above the fill level 92 of the column of material 94,so that inert gas is blown into the process space 22 there above thecolumn of material 94.

Transport components such as blowers, gas pumps and the like requiredfor transport of protective gas, inert gas or offgas and associatedconduits and also control devices are not individually shown in theinterest of simplicity.

The furnace 10 is then operated as follows:

Before first start-up, the process space 22 and the process spaceatmosphere present there firstly have to be freed of oxygen andmoisture, in particular due to air present. For this purpose, theprocess space 22 is flushed with the inert gas and the gas space 80 andalso the insulating annular space 68 are flushed with protective gas.

The heating device 46 is activated, and graphitizable material 14 is fedinto the process space 22 to a fill level 92 by means of the feedconveyor 34. When the output conveyor 44 is then activated, this firstlyconveys incompletely reacted material out of the process space 22 untilgraphite 12 obtained in the heating zone 28 reaches the output conveyor44.

In the ongoing graphitization process, graphitizable material 14 iscontinuously fed into the process space 22 by means of the feed conveyor34 and graphite 12 obtained therefrom is continuously removed from theprocess space 22 by means of the output conveyor 44. Here, the samevolume of graphitizable material 14 is fed in per unit of time, forexample per minute, as the volume of graphite 12 which is discharged perunit of time, i.e. possibly per minute, so that the fill level 92 in theprocess tube 92 remains largely constant. The furnace 10 viewed overallin terms of material management is thus operated continuously here.

In a modification, the furnace 10 is, viewed overall in terms ofmaterial management, operated intermittently. In this case,graphitizable material 14 is, with simultaneous feeding and discharge,continuously fed into the process space 22 by means of the feed conveyor34 and graphite 12 obtained therefrom is continuously removed at thesame time from the process space 22 by means of the output conveyor 44when a material replacement operation in which a particular volume ofgraphite 12 is taken off and replaced by a corresponding volume ofgraphitizable material 14 is carried out.

In continuous furnace operation, the conveying speeds of the feedconveyor 34 and of the output conveyor 44 are in any case set such thatthe residence time of the graphitizable material 14 in the heating zone28 at about 3000° C. is from about 2 to 3 hours. Graphite 12 which is nolonger mixed with graphitizable material may in this case already bepresent in a lower region of the heating zone 28.

At a temperature in the heating zone 28 of about 2700° C., the residencetime of the graphitizable material 14 can be from about 10 to 20 hours.

FIG. 1 illustrates a process procedure in which the fill level 92 in theprocess tube 16 corresponds to the height level of the upper end 28 a ofthe heating zone 28. In other words, a column of material 94 whichextends from the fill level 92 downward and also through the outlet zone26 to the exit 40 of the process tube 16 is formed in the total heatingzone 28. The inlet zone 24, by contrast, is passed through only bygraphitizable material 14 which, after having been fed through theentrance 30 into the process space 22, trickles from the top through theinlet zone 24 onto the column of material 94 and then becomes part ofthe column of material 94. The term trickling is intended here as ageneral term for the material falling downward without any relationshipto possible technical parameters such as flowability of bulk materialsor the like.

FIG. 2 illustrates an alternative way of carrying out the process, inwhich the fill level 92 is located below the upper end 28 a of theheating zone 28. The column of material 94 is thus not formed in thetotal heating zone 28. Rather, a falling heating zone 96, in whichgraphitizable material 14 enters at the top from the inlet zone 24 andtrickles or falls further through the falling heating zone 94 onto thecolumn of material 94, and then arrives on the column of material 94 andbecomes part of the latter, is formed between the column of material 94,i.e. the fill level 92, and the upper end 28 a of the heating zone 28.The falling heating zone 94 is thus passed through by the graphitizablematerial 14 while falling or when falling from the top downward.

In the mode of operation described here, the falling heating zone 96 isa type of free-fall heating zone which is passed through by thegraphitizable material 14 in free fall from the top downward. Here, thecountercurrent flow of the atmosphere in the process tube 16 in thedirection of the offgas outlet connection 90 can retard the falling ofthe particles of the graphitizable material 14 compared to a free falland can thus increase the residence time in the falling heating zone 96.In the modification discussed above, in which the offgas outletconnection 90 is provided at the bottom of the process tube 16, the gasstream can consequently accelerate the falling of the particles of thegraphitizable material compared to a free fall and thereby reduce theresidence time in the falling heating zone 96.

In modifications which are not shown individually, inert gas canoptionally be blown in countercurrent against or in a flow in thefalling direction into the falling heating zone 96 in a targeted mannerin order to deliberately retard or accelerate the speed of falling ofthe particles of the graphitizable material 14 in order to set theresidence time in the falling heating zone 96 in a targeted manner.

That region of the heating zone 28 in which the column of material 94 isformed defines a standing heating zone 98 which is encompassed by theheating zone 28. The term “standing” is merely intended to indicate thatthe column of material 94 as such is present largely stationary, eventhough the column of material 94 is altered due to the introduction ofmaterial and discharge of material during operation of the furnace 10.At least essentially the same temperature prevails in the fallingheating zone 94 and in the standing heating zone 98.

In the falling heating zone 94, the graphitizable material 14 is alreadyheated while it trickles in and reaches the column of material 94already with a higher initial temperature than in the case of a columnof material 94 having a fill level 92 at the upper end 28 a of theheating zone 28. As a result, particles of the graphitizable material 14attain the temperature necessary for graphitization more quickly.

In the variant shown in FIG. 2, the falling heating zone 96 and thestanding heating zone 98 each cover about 50% of the heating zone 28. Inpractice, effective graphitization was able to be achieved in a furnace10 in which the falling heating zone 96 covers from 10% to 60%,preferably from 20% to 55%, more preferably from 30% to 50%, inparticular 30% or the illustrated 50%, of the heating zone 28.

FIG. 3 shows a furnace 10 according to a second exemplary embodiment, inwhich two process tubes 16.1 and 16.2 extend through the insulatinghousing 56. This exemplary embodiment also illustrates furthermodifications in which more than two process tubes 56 are present andextend in a corresponding manner through the insulating housing 56.

In FIG. 3, not all components and constituent parts are provided withreference designations in the interest of simplicity; labeled componentsand constituent parts which correspond to the components and constituentparts in FIGS. 1 and 2 are provided with the same referencedesignations, the association with the first process tube 16.1 or withthe second process tube 16.2 optionally being indicated by acorresponding index 0.1 or 0.2.

The protective housing 64 surrounds both process tubes 16.1, 16.2 here,but it is also possible for a separate protective housing 64 to beassigned to each process tube 16.1, 16.2.

FIG. 3 also shows that the process tubes 16.1, 16.2 are in contact withone another; however, in one modification, which is illustrated in FIG.4, the process tubes 16.1, 16.2 can also be at a distance from oneanother, so that carbon black is also arranged between the process tubes16.1 and 16.2; the annular space 68 is appropriately modified. Thesurrounding housing and associated passages and openings are modifiedaccordingly. There are therefore two protective housings 64 and annularspaces 66 present, and there are likewise two upper connection caps 70and two lower connection caps 74, without all components occurring twiceeach bearing reference designations in the figure.

In the exemplary embodiment shown in FIG. 3, each process tube 16.1,16.2 is assigned in each case a separate feed conveyor 34.1 and 34.2,respectively, and in each case a separate output conveyor 44.1 and 44.2,respectively. In one modification, there can also be only a single feedconveyor 34 present which supplies both process tubes 16.1, 16.2 withmaterial. Accordingly, there can also be only a single output conveyor44 present which takes up graphite 12 from both process tubes 16.1, 16.2and discharges it.

When more than two process tubes 16 are present, a single feed conveyor34 can supply only one, a pair or groups of three or more process tubes16 and optionally all process tubes 16 with graphitizable material 14.In a corresponding way, in the case of more than two process tubes 16, asingle output conveyor 44 can take up graphite 12 obtained from onlyone, a pair or groups of three or more process tubes 16 and optionallyall process tubes 16 and discharge it.

When two process tubes 16.1, 16.2 are each assigned separate feedconveyors 34.1, 34.2 and separate output conveyors 44.1, 44.2, theprocess tubes 16.1, 16.2 can be supplied with different graphitizablematerials 14 which require different residence times in the respectiveheating zone 28.1, 28.2 or a standing heating zone 98, with the latterbeing shown only in the form of the standing heating zone 98.2 in thecase of process tube 16.2 in FIG. 3. This demonstrates that differentprocess tubes 16.1, 16.2 can also be operated in different modes ofoperation.

Regardless of the total number of process tubes 16, the heating zones28.1, 28.2 of two different process tubes 16.1, 16.2 can have equal ordifferent lengths. When the process tubes 16.1, 16.2 are each operatedwith a falling heating zone 96, the lengths thereof and thus therespective length ratio of falling heating zone 96 to standing heatingzone 98 can also be different.

FIG. 5 illustrates a third exemplary embodiment of the furnace 10, inwhich the graphitizable material 14 is not introduced as such as bulk orflowable material into the process space 22, but instead is conveyed ina container 100 for material through the process space 22 and throughthe heating zone 28. As containers 100 for material, of which only threebear reference designations, crucibles 102 having a crucible lid 104 areprovided in the present exemplary embodiment. A transport system 106 isconfigured in such a way that a carrier 100 for material filled withgraphitizable material 14 can be conveyed along the path through theentrance 30 into the process space 22, from there through the processspace 22 to the exit 40 and along the path through the exit 40 out ofthe process space 22.

For this purpose, the transport system 106 comprises the feed conveyor34 and the output conveyor 44, which in this exemplary embodiment areconfigured in such a way that they convey containers 100 for materialcontaining material. In addition, the transport system 106 comprises aprocess space conveyor 108 which is likewise configured in such a waythat it conveys containers 100 for material containing material in theprocess space 22, and conveys the containers 100 for material from theentrance 30 to the exit 40.

In addition, the transport system 106 in the present exemplaryembodiment is designed as loop transport system and for this purposecomprises a connecting conveyor 110, by means of which containers 100for material can be conveyed from the output conveyor 44 to the feedconveyor 34.

The feed conveyor 34 and the output conveyor 44 are here designed asrotary conveyors 112 and 114 which each comprise a rotary element 116and 118, respectively, which can be rotated around a respective verticalaxis of rotation 120. The process space conveyor 108 and the connectingconveyor 110 are designed as linear conveyors 122 and 124, for whichpurpose a pushing device 126 having a powered pushing element 128, herein the form of a push rod, is present in each case. In the case of theprocess space conveyor 108, the pushing element 128 pushes a container100 for material which has entered the process space 22 into the inletzone 24. This container 100 for material then strikes against thecontainer 100 for material located underneath, as a result of which allcontainers 100 for material present in the process space 22 are pushedone place further on. For this to function, a vacant position without acontainer 100 for material is present at the exit 40 of the processspace 22 at this point in time.

When the containers 100 for material pass through the heating zone 28 onthe path through the process space 22, the graphitizable material 14 isgraphitized to give graphite 12. A container 100 for material at theexit 40 consequently contains graphite 12. When a container 100 formaterial has arrived at the exit 40 of the process tube 16, a vacantposition is formed at the entrance 30, so that a container 100 formaterial laden with graphitizable material 14 can there be conveyed intothe process space 22 by means of the feed conveyor 34. Here, at the endof the transport path of the connecting conveyor 110, a vacant positionis produced on the feed conveyor 34 into which an empty container 100for material is then pushed by means of the connecting conveyor 110which operates in the same way as the process space conveyor 108. Avacant position which then arises at the entrance of the connectingconveyor 110 is filled with an empty container 100 for material by meansof the output conveyor 44 when the latter takes the container 100 formaterial laden with graphite 12 from the process tube 16.

The feed conveyor 34 comprises a charging station 130 by means of whichan empty container 100 for material can be filled with graphitizablematerial 14. The output conveyor 44 comprises an emptying station 132 bymeans of which graphite 12 can be taken from a container 100 formaterial. Suitable lock designs are employed here in order to preventcontamination of the furnace atmosphere with foreign atmosphere.

Under the circumstances illustrated in FIG. 5, the rotary elements 116and 118 on four accommodation positions for containers 100 for materialare designed so that a rotation by 90° about the axis of rotation 120 isperformed in each step. The charging station 130 is reached in this caseby an empty container 100 for material one step before the entrance 30of the process tube 16, and the emptying station 132 is reached by acontainer 100 for material filled with graphite 12 one step after theexit 40 of the process tube 16.

In the process space 22, the containers 100 for material areconsequently conveyed intermittently in the case of the furnace 10described. In one modification and with a correspondingly designedtransport system 106, the containers 100 for material can also beconveyed continuously in the process space 22.

In all the exemplary embodiments described above, the temperature in theheating zone 28 or the temperature of the column of material 94 ismonitored by means of a temperature monitoring device.

For this purpose, the temperature is determined at the upper end 28 a ofthe heating zone 28 and/or in approximately the middle of the heatingzone 28 and/or at the lower end 28 b of the heating zone 28 of eachprocess tube 16 present.

As an alternative or in addition, a temperature measurement can also bemade from above at the fill level 92 of the column of material 94.

The temperature measurements are preferably carried out using apyrometer with a pyrometer tube, as is known per se, with the measuringend of the pyrometer tube being arranged at the respective measurementposition. The measurement is preferably carried out at the side of theheating device 46.

For the measurement at the heating zone 28, the pyrometer tube runs, forexample, from the outside through the outer wall of the insulatinghousing 56 and also through the insulating annular space 66 and throughthe wall of the protective housing 64 into the annular space 66 tobefore the outer tube wall 18 of the process tube 16. The associatedpyrometer is positioned at the free end of the pyrometer tube on theoutside of the protective housing 56. Corresponding pyrometer tubes arepreferably arranged horizontally. From the temperature determined inthis way on the outside of the process tube, the temperature can

If a measurement is to be carried out at the top at the fill level 92 ofthe column of material 94, a pyrometer tube extends from above into theprocess tube 16 to just above the fill level 92. The pyrometer tube thenpreferably runs vertically and the pyrometer is correspondingly arrangedat the top on the pyrometer tube. However, a horizontal arrangement ofthe pyrometer tube is also possible. In this case, however, thepyrometer tube also penetrates through the outer tube wall 18 of theprocess tube 16 and opens into the process space 22.

What is claimed is:
 1. A process for producing graphite in a vertical graphitization furnace, comprising: at least one process space which delimits a heating zone, in which a) a temperature of from 2200° C. to 3200° C. is generated in the heating zone; b) particulate graphitizable material is fed through an entrance into the process space; c) graphitizable material is conveyed through the heating zone of the process space, in which it is graphitized to give graphite; d) graphite obtained is discharged from the process space through an exit; wherein as variant A, graphitizable material whose particles have a particle size of less than 3 mm is used; and/or as variant B, a column of material is formed in the total heating zone of a particular process space, with graphitizable material which has been fed in through the entrance trickling from the top through an inlet zone of the process space onto the column of material; and/or as variant C, a column of material is formed in a standing heating zone of a particular process space, said standing heating zone being encompassed by the heating zone, and graphitizable material which has been fed in through the entrance trickles from the top through a falling heating zone, which is likewise encompassed by the heating zone, onto the column of material; and/or as variant D, graphitizable material is conveyed in one or more containers for material through a particular process space and through the heating zone thereof.
 2. The process as claimed in claim 1, wherein the same volume of graphitizable material is fed into a particular process space per unit of time as the volume of graphite which is discharged from this process space per unit of time.
 3. The process as claimed in claim 1, wherein the graphitizable material is fed continuously or intermittently into a particular process space and graphite is discharged continuously or intermittently from this process space.
 4. The process as claimed in claim 1, wherein a fill level of the column of material is kept largely constant in the case of variant B and/or in the case of variant C.
 5. The process as claimed in claim 1 in variant C, a gas is blown in countercurrent opposite to or in a flow in the falling direction of the graphitizable material into the falling heating zone.
 6. The process as claimed in claim 1, wherein a graphitization furnace which has a plurality of process spaces and whose plurality of process spaces are operated in parallel in time is used.
 7. The process as claimed in claim 1, wherein the particles of the graphitizable material have an average particle diameter of greater than 5 μm and less than 3000 μm, or in that the particles of the graphitizable material have an average particle diameter of from 5 μm to 3000 μm.
 8. The process as claimed in claim 1, wherein the temperature of the heating zone is determined, in an upper end of the heating zone and/or in approximately a middle of the heating zone and/or at a lower end of the heating zone and/or at the column of material of each process tube present.
 9. A vertical graphitization furnace having at least one process space which delimits a heating zone, comprising: a) a heating device by means of which a temperature of from 2200° C. to 3200° C. can be generated in the heating zone; b) a feed conveyor by means of which particulate graphitizable material can be fed through an entrance into the process space; where c) graphitizable material can be conveyed through the heating zone of the process space, in which it is graphitized to give graphite; d) an output conveyor is present, by means of which graphite obtained can be discharged from the process space through an exit; wherein e) the heating zone in at least one process space comprises a falling heating zone and a standing heating zone which are configured such that a column of material is formed in the standing heating zone and graphitizable material which has been fed in through the entrance can trickle from the top through the falling heating zone onto the column of material; and/or f) a transport system is present, by means of which graphitizable material can be conveyed in one or more containers for material through at least one process space and through the heating zone thereof.
 10. The vertical graphitization furnace as claimed in claim 9, wherein the feed conveyor and the output conveyor are configured in such a way that they convey containers for material containing material, and the transport system comprises a process space conveyor which is configured in such a way that it conveys containers for material from the entrance to the exit.
 11. The vertical graphitization furnace as claimed in claim 10, wherein the transport system is a loop transport system and comprises a connecting conveyor by means of which containers for material can be conveyed from the output conveyor to the feed conveyor.
 12. The vertical graphitization furnace as claimed in claim 1, wherein the containers for material are crucibles having a crucible lid.
 13. The vertical graphitization furnace as claimed in claim 1, wherein a plurality of process spaces are present.
 14. The vertical graphitization furnace as claimed in a temperature monitoring device is provided, by means of which it is possible to determine the temperature of the heating zone, in particular at an upper end of the heating zone and/or in approximately a middle of the heating zone and/or at a lower end of the heating zone and/or at the column of material of each process tube present.
 15. The process as claimed in claim 1, wherein the particles of the graphitizable material have an average particle diameter of less than 2500 μm.
 16. The process as claimed in claim 15, wherein the particles of the graphitizable material have an average particle diameter of less than 2000 μm.
 17. The process as claimed in claim 16, wherein the particles of the graphitizable material have an average particle diameter of less than 1000 μm.
 18. The process as claimed in claim 17, wherein the particles of the graphitizable material have an average particle diameter of less than 500 μm.
 19. The process as claimed in claim 1, wherein the particles of the graphitizable material have an average particle diameter of from 500 μm to 2000 μm.
 20. The process as claimed in claim 1, wherein the particles of the graphitizable material have an average particle diameter of from 1000 μm to 1500 μm. 